The X pipe uses the pulses of the opposing cyclinders for better scavanging. It acts like a jet pump to pull the exhaust from the other pipe and give it two exits. The straight pipes are just that, straight pipes. The rattles people are hearing may actually be afterburning in the pipes which is cause by too much back pressure. It could also shattered catilytic converters rattling in thier cases (could also be from too much back presuure).

The stock resonator probably has less back pressure than the staright pipes. Each cylinder impulse is carried to the resonator by it's respective pipe (left or right); but, then it has two different exits to go out after the resonator (left and right muffler). With the straight pipes it's left or right the whole way back.

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2007 Suzuki Vinson 500 4X4
2007 Toro 6.5hp
2006 BMW X5 4.4 ltr (his)
2001 BMW X5 4.4 ltr (hers)
1994 Honda XR650L
1984 Honda XR80

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